The maintainer fixes bugs of the part. Particularly, they should fix
security vulnerabilities as soon as possible.

They handle issues related the module on the Redmine or ML.

They may be discharged by the 3 months rule [ruby-core:25764].

They have commit right to Ruby's repository to modify their part in the
repository.

They have “developer” role on the Redmine to modify issues.

They have authority to decide the feature of their part. But they should
always respect discussions on ruby-core/ruby-dev.

A submaintainer of a module is like a maintainer. But The submaintainer
does not have authority to change/add a feature on his/her part. They need
consensus on ruby-core/ruby-dev before changing/adding. Some of
submaintainers have commit right, others don't.